The present invention relates to an electrosurgical instrument and related system for use in surgical ablation or electrocautery procedures. More particularly, it relates to a fluid-assisted electrocautery instrument designed to be indifferent to rotational orientation and including a bendable shaft capable of independently maintaining a desired shape.
A wide variety of surgical procedures involve ablation or cauterization of selected tissue. For example, hemorrhoid or varicose vein removal can be accomplished by ablating the tissue in question. Additionally, tissue ablation and/or cauterization is commonly employed for the surgical treatment of cardiac arrhythmia, and in particular atrial fibrillation. In general terms, cardiac arrhythmia relates to disturbances in the heart's electrical system that causes the heart to beat irregularly, too fast or too slow. Irregular heartbeats, or arrhythmia, are caused by physiological or pathological disturbances in the discharge of electrical impulses from the sinoatrial node, in the transmission of the signal through heart tissue, or spontaneous, unexpected electrical signals generated within the heart. One type of arrhythmia is tachycardia, which is an abnormal rapidity of heart action. There are several different forms of atrial tachycardia, including atrial fibrillation and atrial flutter. With atrial fibrillation, instead of a single beat, numerous electrical impulses are generated by depolarizing tissue at one or more locations in the atria (or possible other locations). These unexpected electrical impulses produce irregular, often rapid heartbeats in the atrial muscles and ventricles. As to the location of the depolarizing tissue, it is generally agreed that the undesired electrical impulses often originate in the left atrial region of the heart, and in particular in one (or more) of the pulmonary veins extending from the left atrium. With this in mind, and as an alternative to drug therapy, ablation of the abnormal tissue or accessory pathway responsible for the atrial fibrillation has proven highly viable.
Regardless of exact application, ablation or cauterization of tissue is typically achieved by applying a destructive energy source to the target tissue, including radiofrequency electrical energy, direct current electrical energy, and the like. The ablative energy source is provided by an electrode that is otherwise placed in contact with the target tissue. For some treatments, the electrode can be formed as a part of a catheter that is otherwise sub-cutaneously delivered to the target site. While relatively non-invasive, catheter-based treatments present certain obstacles to achieving precisely located, complete ablation lesion patterns due to the highly flexible nature of the catheter itself, the confines of the surgical site; etc.
A highly viable alternative device is the hand-held electrosurgical instrument. As used herein, the term “electrosurgical instrument” includes a hand-held instrument capable of ablating tissue or cauterizing tissue, but does not include a catheter-based device. The instrument is relatively short (as compared to a catheter-based device), and rigidly couples the electrode tip to the instrument's handle that is otherwise held and manipulated by the surgeon. The rigid construction of the electrosurgical instrument requires direct, open access to the targeted tissue. Thus, for treatment of atrial fibrillation via an electrosurgical instrument, it is desirable to gain access to the patient's heart through one or more openings in the patient's chest (such as a sternotomy, a thoracotomy, a small incision and/or a port). In addition, the patient's heart may be opened through one or more incisions, thereby allowing access to the endocardial surface of the heart.
Once the target site (e.g., right atrium, left atrium, epicardial surface, endocardial surface, etc.) is accessible, the surgeon positions the electrode tip of the electrosurgical instrument at the target site. The tip is then energized, ablating (or for some applications, cauterizing) the contacted tissue. A desired lesion pattern is then created (e.g., portions of a known “Maze” procedure) by moving the tip in a desired fashion along the target site. In this regard, the surgeon can easily control positioning and movement of the tip, as the electrosurgical instrument is rigidly constructed and relatively short (in contrast to a catheter-based ablation technique).
Electrosurgical instruments, especially those used for the treatment of atrial fibrillation, have evolved to include additional features that provide improved results for particular procedures. For example, U.S. Pat. No. 5,897,553, the teachings of which are incorporated herein by reference, describes a fluid-assisted electrosurgical instrument that delivers a conductive solution to the target site in conjunction with electrical energy, thereby creating a “virtual” electrode. The virtual electrode technique has proven highly effective in achieving desired ablation while minimizing collateral tissue damage. Other electrosurgical instrument advancements have likewise optimized system performance. However, a common characteristic associated with available electrosurgical instruments is a “designed-in” directional orientation. That is to say, electrosurgical devices, and especially those used for atrial fibrillation treatment procedures, are curved along a length thereof, as exemplified by the electrosurgical instrument of U.S. Pat. No. 5,897,553. In theory, this permanent curved feature facilitates the particular procedure (or lesion pattern) for which the electrosurgical instrument is intended. Unfortunately, however, the actual lesion pattern formation technique and/or bodily structure may vary from what is expected, so that the curve is less than optimal. Additionally, the pre-made curve may be well suited for one portion of a particular procedure (e.g., right atrium ablation pattern during the Maze procedure), but entirely inapplicable to another portion (e.g., left atrium ablation during the Maze procedure). As a result, the electrosurgical instrument design may actually impede convenient use by a surgeon.
Electrosurgical instruments continue to be highly useful for performing a variety of surgical procedures, including surgical treatment of atrial fibrillation. While certain advancements have improved overall performance, the accepted practice of imparting a permanent curve or other shape variation into the instrument itself may impede optimal usage during a particular procedure. Therefore, a need exists for an electrosurgical instrument that, as initially presented to a surgeon, is indifferent to rotational orientation, and further is capable of independently maintaining a number of different shapes as desired by the surgeon.